This invention relates to relief object image generators, and more particularly, to use of relief object image generators with computer systems.
Systems for generating images of relief objects are known. Relief objects are objects having a surface with features typically formed by areas and sections lying both within and outside a single two-dimensional geometric plane. A common relief object imaged by known technology is the surface of the human finger which contains ridges and valleys forming a fingerprint. These known systems include a platen to which a relief object is pressed to expose the ridges (areas of the fingerprint which contact the platen) and valleys (areas of the fingerprint which do not contact the platen) of the relief object to imaging equipment. The platen is illuminated by a light source. In many relief object imaging systems, the light from the light source is passed through a collimator before it illuminates the platen. The light is typically coupled through a right-angle prism to the platen at or near an angle corresponding to Total Internal Reflection (TIR). The frustration of TIR and the resulting absorption of light occurs at the ridges of the relief object where the relief object actually makes contact with the platen, thereby creating dark areas corresponding to these ridges. TIR remains undisturbed at the valleys of the relief object where no physical contact with the relief object occurs so illuminated patterns corresponding to the valleys are generated. Thus, light from the light source is modulated by the structural features of the relief object pressed against the platen and this modulated light is transmitted through the platen to an optical system. The optical system is usually comprised of lenses and other optical treating components. The optically treated, modulated light then impinges on a sensor array which converts the optical energy into electrical energy. The intensity at each element of the sensor array is typically converted to a digital value and the values for the array elements may then be processed by a computer for classification or verification of the relief object.
These known relief object imaging systems have a number of disadvantages. For one, each requires a light generating source which must be located at a distance from the platen so that a substantial portion of the platen surface is illuminated by the light source. Additionally, the optically treating elements are typically placed at a distance and angle from the platen to receive the reflected light from the platen. To optimize the benefits of the optical element processing, the optical treating elements must be located at distances from the platen where light rays converge or other known optical physical phenomena occur. Thus, the geometry of known relief object imaging systems impose size constraints which limit the applications for known relief object imaging systems.
Another disadvantage of known imaging systems are distortions of the reflected image. For example, the platen and sensor array in a typical relief object imaging system are tilted to maintain good focus while also maintaining platen illumination near the TIR angle. This tilting causes a type of distortion known as a keystone distortion, which is an apparent shortening of one side of the image due to an asymmetrical magnification factor imposed by this tilt angle. The resulting optical aberration causes the relief object image generator to create a trapezoidal image from a square object. Frequently, this distortion is reduced by interposing optical elements between the sensor array and the platen. However, the interposing of additional optical treating elements exacerbates the geometric constraints for the system and further impacts the applications in which the system may be used.
Known relief object image generating systems are also sensitive to ambient light entering the platen from the surface on which the relief object is placed. Additionally, the presence of an excessive amount of moisture or oil on the relief object alters the modulation of the light by the relief object and may further degrade the image of the relief object in such systems. Likewise, an exaggerated absence of moisture and other fluids in a relief object, such as a fingerprint, may also alter the light modulation produced by the relief object and degrade the image of the relief object. Also, systems which are engineered to address image degradation caused by excessive moisture may not adequately correct degradation caused by excessively dry relief objects and vice versa.
Other known relief object image generators which are not based on light emission principles replicate fingerprint images using direct capacitive coupling between the finger and an electrical sensor. These devices typically suffer from sensitivity to electrostatic discharge environments and can typically be severely damaged through abrasion. The greatest disadvantage with these devices is the cost of these relief object image generators which render the wide scale integration of these devices into computer systems economically impractical.
Computer security is an increasingly important concern as computers become smaller and personal computer inter-connectivity proliferates. The mobility and enhanced capabilities of computers provide computational resources at sophisticated levels as well as at previously unknown locations and situations. These advancements make unauthorized computer access more likely because effective physical control is more difficult to exercise over small portable computers than stationary computers and open networks like the Internet make logical access to computers easier. One way to frustrate the purpose of computer thieves is to deny them, or the persons to whom they sell the computers, the ability to use the computer. Most computer access control systems use a password or other secret tokens that an authorized user enters to activate a computer system. However, most computer thieves can disable password protection or similar security access features so the computer may be used by someone other than an authorized person. While there are known systems for limiting access to valuable resources by identifying authorized persons with fingerprint imaging systems, known relief object image generators do not possess physical geometrical dimensions which render them compatible with laptop computers and the like for reasons discussed above.
Associated with the increasing need to enhance computer access security is the need to accomplish much of the typical computer/user interface functionality in a more compact, cost effective and ergonomically efficient manner. That is, as the footprint of portable computers decreases, the area available for the keyboard, function keys and cursor control devices also decreases. Thus, a need is arising for a cursor controller that requires less area of a keyboard than known touchpads or that can be integrated with other functional components of a user""s keyboard.
What is needed is a relief object imaging system for performing security and access control functions that may be incorporated in different types of computer systems used in a variety of applications.
What is needed is a device that integrates the control of function keys with the function of a cursor control device.
The above identified limitations and disadvantages of previously known computer access control devices are overcome by a system made in accordance with the principles of the present invention. A computer access control system made in accordance with the principles of the present invention includes a relief object generator which is comprised of a single electrode electroluminescent device coupled to an alternating current source to generate an image corresponding to a relief object placed against the relief object image generator, a sensor array for receiving the generated image and converting the image to electrical signals, a memory for storing image data corresponding to a relief object associated with an authorized user, and an image processor for generating image data corresponding to the electrical signals received from the sensor array and for comparing the stored image data to the generated image data, the image processor generating an access granted signal in response to the stored image corresponding to the generated image data. Preferably, the image data generated by the processor of the access control device is descriptive information that corresponds to the generated image and the image data stored in the memory is descriptive information that corresponds to the relief object image associated with the user.
A computer control device made in accordance with the principles of the present invention includes a relief object image generator coupled to a computer for user access, the relief object image generator for generating images of a relief object brought in proximity to the relief object image generator, a sensor array for receiving the generated images and converting the images to electrical signals corresponding to the received images, and an image processor for converting the electrical signals received from the sensor array to computer control signals. A computer control device made in accordance with the principles of the present invention may control a computer function by processing relief object image changes to generate function select or activation signals. For example, the image processor may generate a select signal in response to the image processor detecting the presence and absence of a relief object image generated by the relief object image generator. As another example, the image processor may control a xe2x80x9cclickxe2x80x9d operation by generating a xe2x80x9cclickxe2x80x9d function control signal in response to the image processor detecting a presence, absence, and renewed presence of a relief object image generated by the relief object image generator. To control operational parameters for a computer system, the image processor of the computer control device of the present invention, may generate an operational parameter control signal in response to movement of a relief object image generated by the relief object image generator. By adding memory to the computer control device and storing information corresponding to authorized individuals, the computer control device may also be used as a computer access control device as described above.
The relief object image generator used in the computer access control device of the present invention has a reduced geometry and the ability to incorporate other functions required for computer operation by using a single electrode electroluminescent device and an electrical current source. The electroluminescent device may be an inorganic or organic electroluminescent device. With an electroluminescent device, the electrical current source has one lead coupled to the single electrode of the electroluminescent device and a second lead coupled to a relief object in proximity to the electroluminescent device. This electroluminescent device provides current to the relief object and the current is strongly coupled from the relief object to the single electrode electroluminescent device by ridges of the relief object while the current is weakly coupled to the electroluminescent device by the valleys of the relief object. Those areas of the electroluminescent device which are strongly coupled to the current from the relief object generate light which is more intense than the areas of the electroluminescent device which are weakly coupled to the current from the relief object. The light generated by the electroluminescent device in correspondence with the valleys and ridges of the relief object forms an optical image of the relief object. The electrodes in known electroluminescent devices are typically planar and are used to provide a light field that corresponds to the aligned areas of the electrodes. By fabricating the electroluminescent device with a single electrode and coupling the current source to a relief object held against the single electrode electroluminescent device, the amount of current coupled to different areas of the electroluminescent device varies in correspondence with the valleys and ridges of the relief object and generates an image of the relief object.
An organic single electrode electroluminescent device creates an image of a relief object as described above. However, as these devices typically require lower voltage but higher current than that required for inorganic electroluminescent devices, they may include a pressure-variable impedance layer and a flexible conductive layer. In this implementation, the second lead of the current source is connected to the flexible conductive layer overlaying the impedance layer such that the pressure generated by the ridges of the relief object pressing against the flexible conductive layer form current paths in the impedance layer and, correspondingly, an image of those ridges. Preferably, direct current (DC) sources are used with organic electroluminescent devices and alternating current (AC) sources are used with inorganic electroluminescent devices.
The optical image generated by the system of the present invention may be processed by optical elements and provided to a sensor array. Typically, the optical elements include reduction lenses which reduce the size of the image and, correspondingly, the size of the sensor array used to convert the image to electrical signals. Sensor arrays used in these embodiments of the present invention may be integrated circuits or the like. Using reduction lenses to reduce the size of the image, and correspondingly, the integrated circuit sensor, saves cost as the integrated circuit is made of silicon which has a cost directly proportional to the physical surface area of the integrated circuit. In another embodiment of the present invention, a one-to-one sensor array is located proximate to the single electrode electroluminescent device. The one-to-one sensor array has a length and width which is approximately the same as the electroluminescent device. The one-to-one sensor array may be made of a semiconductor material on an insulating substrate, such as amorphous silicon on glass. Because the sensor array is proximate to the electroluminescent device, the thickness of the computer access control device of the present invention is substantially smaller than previously known systems that require an optical element to focus light reflected from a platen onto a sensor array. Additionally, the sensor array and electroluminescent device are substantially orthogonal to the path of the light generated by the electroluminescent device. As a result, distortion caused by angular placement of the platen and sensor array in previously known systems is essentially eliminated. The ability of the single electrode electroluminescent device to generate light allows the computer access control device of the present invention to operate without an external light source. This further contributes to the reduced size and complexity of the access control device of the present invention.
In a system of the present invention which uses an inorganic single electrode electroluminescent device, the electroluminescent device includes a transparent electrode layer, a dielectric layer, a light emitting layer which is interposed between a first surface of the transparent electrode layer and a first surface of the dielectric layer, and an alternating current source which has a first lead coupled to the transparent electrode layer and a second lead that is proximate to a second surface of the dielectric layer. While the dielectric layer may be translucent, it, preferably, is substantially opaque to attenuate the amount of light transmitted through the second surface of the dielectric layer that is not generated by the relief object such as ambient light. When a relief object is placed in contact with the second surface of the dielectric layer and is coupled to the second lead of the alternating current source, current is strongly coupled from the ridges of the relief object through the dielectric layer and light emitting layer to the transparent electrode while current is weakly coupled from the valleys of the relief object to the transparent electrode. The light emitting particles in the strongly coupled current path generate light more intensely than those particles in the weakly coupled current path. While the term xe2x80x9ctransparentxe2x80x9d is used to describe the electrode layer of the electroluminescent devices used in the systems made in accordance with the principles of the present invention, the reader should understand that as long as sufficient light is passed by the electrode so a relief object image or descriptive information about a relief object image can be generated, the electrode is adequately xe2x80x9ctransparent.xe2x80x9d Thus, the term xe2x80x9ctransparentxe2x80x9d refers to both transparent and translucent materials as those terms are typically understood.
A relief object relief generator used in a computer control device made in accordance with the principles of the present invention does not require an external light source or a collimator as no light is required for platen illumination. Instead, a relief object causes the single electrode electroluminescent device to generate a self-luminous optical image of the relief object when the relief object is coupled to the current source and brought in contact with the single electrode electroluminescent device. Because the light is generated by the structure and not illuminated by a light source, the sensor may be placed directly opposite the transparent electrode of the electroluminescent device. No intervening optical elements are required for treating the light to reduce distortion caused by the angles at which the light source, platen and sensor array are located in previously known systems. As a result, the relief object imaging system is much more compact and may be used in computer systems more easily, economically and efficiently than previously known imaging systems. For example, one embodiment of the present invention may be located on a keyboard of a laptop computer to generate an image of a fingerprint which may be processed to generate descriptive information that is distinctive for the fingerprint. The information may be the image itself or a set of algorithmically derived templates which map repeatable fingerprint characteristics that are unique to the individual to which the fingerprint belongs. The descriptive information is compared to stored fingerprint descriptive information to provide access to the computer or converted to digital information and transmitted to another computer for access to another computer system to verify a financial transaction over a network. Thus, the computer access control device of the present invention may be used to generate descriptive data about a relief object at a remote site or to generate an access granted signal based on a local comparison of the descriptive data with stored data. Either the descriptive data or the access granted signal may be transmitted to another computer coupled to an open network. The second computer may use the transmitted descriptive data to verify that the user associated with the relief object at the remote site is authorized to access the second computer. Consequently, security for logical access to computers coupled to an open network is enhanced.
Another inorganic single electrode electroluminescent device that may be used with systems made in accordance with the principles of the present invention includes a transparent electrode layer, a light emitting layer having an exposed outer surface, and an alternating current source which has a first lead coupled to the transparent electrode layer and a second lead that is proximate to the exposed surface of the light emitting layer. When a relief object is placed in contact with the exposed surface of the light emitting layer and is coupled to the second lead of the alternating current source, current is strongly coupled from the ridges of the relief object through the light emitting layer to the transparent electrode while current is weakly coupled from the valleys of the relief object to the transparent electrode. The light emitting particles in the strongly coupled current path generate light more intensely than those particles in the weakly coupled current path. The capacitive effect provided by the dielectric layer in the embodiment discussed above is provided by the capacitance of the relief object especially when the relief object is a person""s finger.
The light emitting layer of the inorganic type of electroluminescent device may include phosphor particles which may be a coating applied and adhered to the first surface of the transparent electrode layer using a binding agent. Alternatively, the light emitting particles may be dispersed throughout a dielectric layer of an inorganic electroluminescent device. In this type of inorganic electroluminescent device, the light emitting particles may also be phosphor particles and the phosphor particles may be encapsulated within a protective dielectric layer to prevent moisture from degrading the phosphor. Preferably, the transparent electrode layer of an inorganic electroluminescent device is comprised of indium tin oxide (ITO) or a zinc oxide:aluminum (ZnO:Al) composite; the phosphor is preferably zinc sulfide:copper (ZnS:Cu) or it may be zinc sulfide:manganese (ZnS:Mn); and the dielectric layer may be barium titanate (BaTiO3). The light emitting layer of this type of inorganic electroluminescent device may also include reflective or refractive particles which cause the light generated by the phosphor to become more directional and, therefore, more concentrated in the direction of the sensor. Empirical measurements indicate that both the frequency and the waveform of the alternating current source may be adjusted to control the contrast between the light generated by the ridges and valleys of the relief object. By adjusting the voltage amplitude of the alternating current source, the average light intensity generated by the phosphors may be varied. Thus, the systems of the present invention using this type of inorganic electroluminescent device provide contrast and intensity control of the light image generated by the relief object image generator.
Another electroluminescent device that may be used with the systems of the present invention includes a pressure-variable impedance layer that covers the dielectric layer, a flexible electrode that covers the variable impedance layer and the second lead from the alternating current source is coupled to the flexible electrode. The variable impedance layer is comprised of conductive and/or capacitive particles dispersed through a non-conducting compressible polymer. Where the ridges of a relief object contact the flexible electrode and generate localized pressure, a conductive path through the impedance layer is formed by bringing conductive/capacitive particles into proximity with one another. Those areas of the flexible electrode proximate and aligned with the valleys of the relief object do not generate significant localized pressure which compresses the conductive/capacitive particles. Thus, the particles remain separated and less current is passed through those portions of the layer. Accordingly, the localized pressure caused by pressing the ridges of the relief object against the flexible electrode provide more current from the alternating current source to the transparent electrode through the dielectric and light emitting layers. Again, the magnitude of the current passing though the light emitting particles determines the intensity of the light for the optical image of the valleys and ridges of the relief object.
Systems using the electroluminescent devices with a pressure-variable impedance layer do not couple current from the alternating current source to the relief object. Instead, the relief object forms conductive/capacitive paths in the variable impedance layer for the current supplied from the flexible electrode. Thus, these systems insulate the relief object from the alternating current. This is especially advantageous for systems incorporating relief object imaging systems that are used in countries having regulations regarding the amount of current to which a person can be exposed. Because pressure from the structure of the relief object generates the conductive/capacitive paths through the variable impedance layer, excessive moisture or dryness does not degrade image contrast as happens in systems where the platen of a relief object image generator must be illuminated.
Systems made in accordance with the principles of the present invention may include an organic electroluminescent device. The structure of the organic electroluminescent device may be comprised of a thin, sublimed molecular film such as tris (8-quinolinolato) aluminum (III), commonly denoted as Alq or a light-emitting polymer with specialized structures which provide positive and negative charge carriers having high mobility. Light-emitting polymers include poly (p-phenylene vinylene) or PPV, soluble polythiophene derivatives, and polyanilene which may be applied to the specialized structure by known coating techniques such as spin or doctor-blade coating.
Because organic electroluminescent devices operate at low voltages, the relatively high self-resistance of common relief objects do not effectively modulate the luminescence generated by the electroluminescent device. If the relief object to be imaged is not capable of withstanding a relatively large voltage drop at currents of at least a few milliamperes, an insulating layer is preferably provided between the relief object and the organic electroluminescent device. Preferably, the insulating layer is a pressure-variable impedance layer such as the one discussed above. The pressure-variable impedance layer selectively provides an electrical impedance which varies in correspondence with the ridges and valleys of the relief object contacting the impedance layer. As a result, the higher level currents may be presented through the lower impedance paths to the organic electroluminescent device to generate holes and electrons which recombine to produce localized photons. More preferably, the organic electroluminescent device is coated with a pixelated low work function metal such as calcium or aluminum to effect efficient electron charge injection. Inventive systems which utilize an organic electroluminescent device provide a relief object image generator which may be powered from a DC current source.
A relief object image generator of the type described above possesses physical geometrical dimensions, relatively lower costs, and environmental robustness which make it compatible with portable computers such as laptop computers, desk-top personal computers, associated peripherals and the like. The relief object image generators discussed above are also compatible with other applications where personal identification numbers (PIN) and passwords are currently used and where volumetric constraints have prevented the practical integration of previously known relief object image generators. Examples of these applications include cellular telephones, keyless entry devices for all applications requiring physical security (including buildings, rooms, automobiles, etc.). Another application where the relief object generators discussed above may be used is a point-of-sale device that verifies a user""s identity using information available from a fixed or portable memory. In this application, fixed memory applies to the memory physically resident with the relief object image generator. Portable memory is any information storage media or device which is not physically resident with the relief object image generator but is typically controlled by the user. This includes, but is not limited to, printed data in the form of symbology, optical laser cards, smart chip cards, passive and active RF cards and magnetic stripe cards.
In a portable computer, a single electrode electroluminescent device is mounted, preferably near the keyboard, so a user may place a finger on the surface of the electroluminescent device. The current source and automatic gain control (AGC) are in electrical connection with the electroluminescent device while the image sensor is located behind and in the optical path of the electroluminescent device. The image generated by the electroluminescent device is converted by the sensor array to electrical signals and then processed by the computer""s processor or an application specific integrated circuit (ASIC) to generate descriptive information that is unique to that fingerprint. The processor or ASIC determines whether the resulting set of fingerprint descriptive information corresponds to one of the sets stored within the computer for authorized users. If the descriptive information corresponds to one of those stored in the computer, the computer is activated. Otherwise, access to the computer is denied. Preferably, the relief object image generator is normally in a xe2x80x9csleepxe2x80x9d mode when the computer is off. By touching the relief object image generator, power is applied to the computer and the authorization process commences. If authorization is verified, the computer is automatically initialized with a predetermined set of programs and connections. Likewise, the relief object generator may be used to obtain an image of a person""s finger so it can be processed and the resulting fingerprint descriptive information transmitted to a remote site and used to authenticate a person from a remote system. For example, an image of a person""s fingerprint may be obtained, processed and transmitted to a banking system for access to a person""s financial account or to view real-time images of one""s child at a daycare center that can be accessed over an open network such as the Internet. In both the remote authentication and local authentication applications, the security afforded by the use of the relief object image generators discussed above may be further enhanced by the employment of an encryption technique for the transmission of the descriptive information and/or the command signifying a successful match. This would help to prevent the intentional or unintentional subversion or corruption of that data.
While the relief object image generator discussed above may be mounted at any suitable location on a computer, preferably, it is mounted in a location convenient for user access. In most portable and desk-top computers, a cursor control device such as a mouse, joystick, direction keys or other variable position/direction indicating device, is placed in such a location. By sizing the relief object image generator so it approximates or is less than that of known cursor control devices, the relief object image generator may be more readily incorporated into computers of current design through the physical replacement of these cursor control devices. Of course, if the relief object image generator physically replaces the cursor control device and all previous functionality is to be retained, the relief object image generator must be capable of accomplishing all functions associated with the replaced cursor control device.
In the cursor control device of the present invention, an image generated by the single electrode electroluminescent device of a relief object image generator is detected by light sensing elements of a sensor array and provided to an image processor. In response to movement of an object or finger imaged by the relief object image generator, a number of the light sensing elements may transition from a light detecting state to a no light detected state or vice versa. The resulting change in the generated image is processed to determine a direction of movement of the relief object and to generate a corresponding directional control signal that causes the display screen pointer to move in a corresponding direction. For example, if a finger is rolled to the user""s right, the left side of the image is no longer detected and the right side of the image increases. This causes the image processor to generate a right directional control signal that is used to move a displayed cursor to the right. In a similar manner, the cursor may be moved in other directions.
The xe2x80x9cclickxe2x80x9d of known mouse devices for highlighting a displayed object may be implemented in the preferred embodiment of the present cursor control device by detecting the absence of a previously detected image and then timing the interval of image absence before the image reappears. If the image reappears before the interval exceeds a predetermined maximum interval length, a xe2x80x9cclickxe2x80x9d operation is implemented. In a similar manner, a xe2x80x9cdouble clickxe2x80x9d operation may also be implemented. Also in a similar manner, both the xe2x80x9cclickxe2x80x9d and xe2x80x9cdouble clickxe2x80x9d operations, as well as other special actions, may be initiated using other combinations of changes to the relief object images and may also be implemented to accomplish the xe2x80x9cclick and dragxe2x80x9d functions of known cursor control devices.
Likewise, a computer control device of the present invention may use a relief object image generator having a pressure-variable impedance layer to generate control signals that implement the xe2x80x9cclick,xe2x80x9d xe2x80x9cdouble-clickxe2x80x9d and xe2x80x9cdragxe2x80x9d functions, as well as other special functions or actions. In these implementations of a computer control device, a gradual increase in pressure caused by the relief object on the flexible conductive layer generates a corresponding increase in the current flowing through the flexible layer that intensifies the image. By sensing this changing intensity and determining when it crosses a predetermined threshold, the processor may detect an image change and generate a control signal to activate a special function such as a xe2x80x9cclick,xe2x80x9d xe2x80x9cdouble-click,xe2x80x9d or xe2x80x9cdragxe2x80x9d function. Functions activated by multiple signals, such as a xe2x80x9cdouble-click,xe2x80x9d may be implemented by detecting repetitive crossings of the image intensity across a single threshold or a series of crossings across multiple thresholds.
The computer control device of the present invention may also be used for operational parameter control. In a manner similar to that discussed above for the cursor control device, the processor may detect changes in the relief object image so a user may select or activate a computer peripheral or subsystem. In a similar manner, the processor may detect other changes to the relief object image as commands to select and adjust specific control parameters for the selected computer peripheral or subsystem. For example, a computer operational control device of the present invention may be mounted in the housing of a computer monitor. An image processor and memory of the control device processes images of a finger or other object produced by the relief object image generator. By employing the xe2x80x9cclickxe2x80x9d and xe2x80x9cdouble-clickxe2x80x9d implementations described above, the user may select a control parameter for the monitor, such as contrast or brightness. For example, rolling a finger on the relief object image generator may produce a changing image that may be processed by the image processor to generate a control signal that selects monitor brightness, for example. Continuing the example, rolling one""s finger to the right may result in the image processor generating a control signal that increases the monitor brightness while processing a finger image rolling to the left may result in a control signal that decreases the monitor brightness.
These and other advantages and benefits of the present invention may be ascertained from the detailed description of the invention presented below and the drawings discussed therein.